We are wanting to convert an existing built-in bookshelf to a back-light shelved unit for displaying glass art etc., ideally in the same manner that galleries use, eg:

The key aspect of such lighting is that the light comes from behind the art, therefore illuminates it in a particular way. (Any lighting that comes from in front of the art will fail for this reason.)

My initial thoughts (to keep the complexity/price down) had been to install LED strip-lighting on the backs of the shelving (which would be not quite touching the back of bookcase), however I'm thinking that will produce shadows and produce quite a different illumination (relying on reflection off the back of the space, which would be painted white). One alternative discussed was to rebate the shelves a bit at the back and run the strip lighting along that, so that the bulbs sit basically flush with the bottom of shelves, however this increases the likelihood of the lights being visible from when viewed from below the height of the shelf, and doesn't solve the problem the light will still be bouncing off the back wall to reflect through the glass.

So, my latest thoughts are to try to replicate using a variation of the way galleries light such shelving, which is using flurorescent tube lighting behind white opaque glass/perspex. My plan is to use LED strip lighting (cheaper/wastes less depth); put in some beading around say 2cm deep x 1cm wide all the way around the back edges of the bookshelf - the strip lighting would then be stuck to the beading, while a sheet of something opaque would be attached to the other exposed side of the beading. As the space is fairly large (at a guess 80 x 210 cm), I'm also thinking of running beading along parallel where the shelving will go - this will allow both a further fixing point for the opaque backing and also another place where LEDs could be run to even out the lighting if needed.

Anyway, I'd appreciate any thoughts as to how this lighting project could be better executed.

I also have no good leads as to what I could use and where I could get something affordable for the back opaque sheeting - I imagine that perspex is fairly expensive? The material needs to be fairly solid as it would need to be sit very flat when attached in the vertical; it would also need to have a uniform level of opaqueness, given the lighing will expose any variation (so painting it myself wouldn't be an option!). It would also need to have some degree of scratch resisitance. Could I get some decently thick plastic sheeting and then have a firm apply a white film to one side of this?

Thanks for the replies. You're right - the cost is not as bad as I had feared. A local shop has sheets 2.4x1.2 for $125+GST @ 3mm thick - will that be thick enough, given it can be supported in as many points as necessary around the outside? (or would this thickness also need the horizontals at the same level as the shelves?). I'm also not sure if the thicker sheets will absorb more light, but am thinking not given I assume it's just a coating that won't vary whichever the thickness.

www.plasticcuttosize.co.nz would do a piece 2.2 x 0.8 for $94 (3mm) or $141 (4.5mm) (not sure about shipping costs yet). I'm going to email one of the key sellers on TM for a price as well.

Colour-wise, the local store has four "white"-backed sheets in stock, and suggests I call in to compare them, but thinks one of the 'opal' colours would be most appropriate for the purpose.

When you say "directly behind it", are you saying essentially run the strip lights on the wall directly behind the acrylic? If so, how many strips would you run down the length of the bookcase, say two?

And would that not potentially lead to being able to see patches of stronger light directly in front of the LEDs? I'd imagine that if I could afford a decent distance between the wall (where the LEDs would be attached in this scenario) and the acrylic that such bright patches wouldn't be a concern, but doing this will reduce the depth (and therefore usefulness) of the shelves. I reckon the location of an LED say only 1 cm from the acrylic would be visible. That's why I was thinking of putting them on the sides and along the top/bottom (where, if necessary, I could even put them behind the beading which the acrylic will attach to, ie coming outwards from the back it would be the wall / LEDs / beading / acrylic.

If it is diffused enough, it should be OK. It is likely you will have dark and bright spots anyway, it is just a case of choosing where you want them.I would try two strips, on at 1/3rd the way down, the other at 2/3rds.

The diffusing acrylic I have seen has a matt finish on the back which seems to help with diffusing (rather than just a glossy white sheet of Acrylic?) Another one I have seen, but it looks a bit difficult to get right, is a strip light under the edge of a clear piece of acrylic, with a white backing sheet stuck to the rear. The light 'bounces' all the way up the inside of the acrylic (internal refraction?).

Disrespective: Be aware that if you don't want to see spots from the led strip that you will still need some depth behind the diffuser. This distance will be dependent on how dense the led's are on the strip though.

You won't need more than 1.5mm thick acrylic to act as a diffuser and it would be able to support its own weight vertically without issue if the span is less than 600mm or so in both directions.

You could edge light the acrylic if you went with thicker stuff, which might give a nice glow to the acrylic if it's not being diffused with a film over the smooth face.

Will you be building these yourself? What sort of tools do you have? A hand router?

Guess it'll be a matter of experimenting with the actual materials (LEDs and the selected acrylic) to determine how visible the source of light is from the front view. But wouldn't it be minimised if the LEDs were placed behind the beading that the acrylic will be attached to? I could even place some narrower beading on which to attach the LEDs, to minimise any shadows created by the LEDS being "hiddden" by the beading for the acrylic (and which would also increase the distance beween LEDs and the acrylic, as opposed to having the LEDs attached just behind the acrylic), eg something like the following (a bird's eye view):

The space is (at a guess) 2.1 x 0.8, but given the thinnest opaque acrylic I can find is 3mm, will that be adequate if supported on all sides? Or will I need the additional horizontals? I'd rather avoid these horizontals, as I think they'll either impede light distribution or, if I put additional LEDS on these, it'll make it unncessarily complex to light evenly. (An alternative is using minimally sized chocks at the levels of the shelving , simply providing enough to surface area to hold the acylic out to the right depth and allow it to be screwed to the wall, which shouldn't impede light flow.)

I'll be doing this with the help of a friend and probably my father-in-law (who has a decent range of tools). I'm trying to keep it relatively simple to minimise the chances of f-ups and keep costs down. My friend wants to have the lights wifi controlled, but that' more than we need! Just a switch and a dimmer should be adequate for our purposes...

In regards to sourcing LED strip lighting - am I safe to pretty much get anything ok looking off eBay or Ali Express, or are there particular sellers I should purchase from? Or should I be buying from within NZ? LEDs seem just so much more expensive when sourced from here.

That looks fine. I think the key to spotless led lighting will be keeping the point sources of light away from the surface of the acrylic. I think you would be best to buy some acrylic and led strip, then do some tests of how far away, or orientation, the led's should be to minimise the spots.

3mm acrylic will be plenty strong enough to hold its weight unless you're getting into about <1200mm high with no fixings i'd reckon.

When you do buy led's, my suggestion is to look for the density of the led's. The denser they are the less spots will be visible. Also consider what colour light you want, cool or warm white, RGB etc. All should be able to be driven by a 12V driver but might not be supplied with one. Looks like a fun project regardless.

Disrespective: That looks fine. I think the key to spotless led lighting will be keeping the point sources of light away from the surface of the acrylic. I think you would be best to buy some acrylic and led strip, then do some tests of how far away, or orientation, the led's should be to minimise the spots.

3mm acrylic will be plenty strong enough to hold its weight unless you're getting into about <1200mm high with no fixings i'd reckon.

When you do buy led's, my suggestion is to look for the density of the led's. The denser they are the less spots will be visible. Also consider what colour light you want, cool or warm white, RGB etc. All should be able to be driven by a 12V driver but might not be supplied with one. Looks like a fun project regardless.

Thanks for the further comments. As per your suggestion, I'll see if I can get a small piece of off-cut acrylic from the supplier here in PN to do some testing before confirming the design.

I've been thinking about colour - my wife's dead against the full colour options (risk of tackiness in this context!), and I also feel these run the risk of the very thing you point out - given the number of different coloured LEDs they need, the LED density for displaying "white" will be fairly low. I'd imagine this will be the same problem with those I've seen on eBay that allow cool/standard/warm whites through having dedicated LEDs (so my concern would be each temp setting would only run 1/3rd of the LEDs at any one time). Neither of us are fans of 'cool' white, and a couple of square metres of this in a room could be very morgue-like. I reckon a "neutral" temperature will probably be ideal, but if it's a binary choice (cold versus warm) I'd select the latter.

I'm thinking also of not lighting up the full length of the space, given the bottom of it is used for an amp and CD player - I think it'll be fairly ugly having the cabling at the back lit up! In this case, I think I'd still take the acrylic down the full length of the space (to provide a consistent look, especially when the lighting's not on), but just panel it off so the lights only start from the first shelf height.

I would at least get cool white-warm white strips. aliexpress for that is really cheap, and you can get the "wifi" controller which has a remote for stuff all as well.

That way you can get the exact effect you are looking for and not be stuck with whatever one you buy. the neutral white 4000k is quite rare in LED strip - its mostly warm white or daylight, so the variable stuff means you can get what you want and can warm it up if that is a problem for SWMBO.

Yep, I think that's inevitable with my proposed design, but I'm not too worried about it as it won't be significant relative to the whole space.

That said, if anyone can propose a method that avoids such a beading I'm all ears! (It would have to allow both for the acrylic to be firmly attached and also ideally provide a way of sheltering the LEDs from pointing out directly).